Gear shifting actuator and method of shifting gear ratios

ABSTRACT

A gear shifting device for shifting gears of a transmission comprises: at least one guide rail each extending in a longitudinal axis thereof; a plurality of shift effecting members (e.g., shift forks or the like) configured to move a plurality of corresponding sliding sleeves coupled to the guide rail for shifting gears upon actuation of a shift actuator, the shift effecting members each having a terminal end portion with a finger receiving opening formed therein, the finger receiving opening extending in a direction generally parallel to the longitudinal axis of the guide rail; and a shift shaft extending in a direction generally parallel to the longitudinal axis of the guide rail, the shift shaft having a shift finger coupled thereto. The shift shaft is rotatable to pivotally position the shift finger at locations aligned with the finger receiving openings of the shift effecting members, and is also displaceable in the longitudinal direction in the finger receiving openings to move the shift effecting members to effect a gear shifting operation. Methods of shifting gears with a gear shifting device are also disclosed.

FIELD OF THE INVENTION

The present invention relates to a shifting apparatus and method forshifting gear ratios in a transmission, and more particularly, to a gearshifting actuator and a method for shifting gear ratios for a dualclutch transmission of a vehicle.

BACKGROUND OF THE INVENTION

A dual clutch transmission of a vehicle typically utilizes two manualshift transmissions in a single housing to drive the wheels of a vehiclewith different gear ratios or stages. A conventional dual clutchtransmission generally contains two independent clutches that arenormally open or released, and further includes at least one inputshaft, and at least one output shaft operably coupled with each other.Each of the two clutches is coupled to its corresponding input shaft todrive an output shaft with selected gear ratios.

In order to perform the gear shifting process, the dual clutchtransmission further includes a gear shift actuating device which isdriven by an actuator such as an electric motor. According to the dualclutch transmission systems known in the art, the gear shifting devicestypically include a drive shaft, a shift finger for the gear engagingoperation, and elements designed particularly for disengaging operationsof the gears. For example, as illustrated in FIGS. 3 a and 3 b, aconventional gear shifting device for double-clutch transmissions knownin the art uses shift frames 301, 302, 303, and 304 to movecorresponding shift members to engage with the gears assigned thereto,and further includes a drive shaft 315 (only a portion shown in FIG. 3a) with a shift finger 316 and a plurality of disengagement cams 316 aformed on the drive shaft 315 for the engagement and disengagementoperation of the gears, respectively. As shown in FIGS. 3 a and 3 b,each shift frame (301, 302, 303, and 304) includes inner cam groove 306of complex contour combined with a generally rectangular cam groove andtwo opposing circular cam grooves formed at two opposite sides of therectangular groove. As shown in FIG. 3 c, which is a sectional viewtaken along the line A-A in FIG. 3 b, the cam groove 306 of each of theshift frames 301-304 has the same width 331 a, the shift finger 316 hasa width 332 a between two opposite sides (shift finger contact sides),which width is smaller than width 331 a of the shift frame.

In order to shift and engage a selected gear, the drive shaft 315 isfirst axially displaced so as to align the shift finger 316 with theshift frame 301-304 (for example, shift frame 304 as shown in FIG. 3 c)of the target gear. The drive shaft 315 is then rotated by actuator, andthe shift finger 316 pushes the selected shift frame by rotational camcontact of the shift finger 316 against the two opposite rectangularsides of cam groove 306 of the selected shift frame, and as aconsequence, the selected shift frame (e.g., shift frame 304) for thetarget gear moves in lateral direction to predetermined distance,namely, either distance 332 b to set one gear ratio or distance 332 c toset a different gear ratio according to the design of the transmission.On the other hand, in order to release or disengage one or morenon-target gears, the drive shaft 315 is again axially moved until theshift finger 316 is aligned with the shift frame (301, 302, 303, or 304)for the gear to be released, and one of the multiple disengagement cams316 a of the drive shaft 315 rotates to a releasing direction and pushesthe cam groove 306 of the shift frame upon rotation of the drive shaft315, and the shift frame for the gear to be released moves in lateraldirection by a predetermined distance to release the releasing gear.

As described above, this conventional gear shifting device requirescomplex cam parts to be manufactured with precision, such as shiftframes 301-304 with complex cam grooves produced in high precision andaccuracy, shift finger 316 with precise cam contour, and multipledisengagement cams 316 a with precise cam contour. Thus, this shiftingdevice requires a complex production process and a high manufacturingcost.

Moreover, as shown in FIG. 3 a, the drive shaft 315 (only a portionshown in FIG. 3 a) extends in a direction perpendicular to the shiftframes 301-304, and as a consequence, also perpendicular to thedirection of the fork guide rails as well. An actuator (not shown) ispositioned at a distal end of the drive shaft 315, and coupled theretoto drive the drive shaft for the gear shifting operation. Due to thisperpendicular arrangement of the drive shaft 315 relative to the forkguide rails, the shifting device requires a relatively large volume, andit is generally difficult to reduce the size of the resultanttransmission containing the shifting device.

In another example, U.S. Pat. No. 7,353,726 (assigned to ZFFriedrichshafen AG.) suggests a shifting device which has a structuregenerally similar to that described above with FIGS. 3 a-3 c. Similar tothe above-described design, this gear shifting device also includes fourgearshift frames of rectangular shape with cam grooves or recessesformed therein, multiple sets of sliding selector shafts affixed to thegearshift frames, and a shift drive shaft which extends in a directionperpendicular to the sliding selector shafts and with a plurality ofshift fingers coupled thereto for engaging and disengaging operation ofthe gears. See FIG. 4 of U.S. Pat. No. 7,353,726.

As describes, this shifting device also requires complex cam parts to beprecisely manufactured, such as four gearshift frames with cam groovesto be produced with high precision and accuracy, multiple shift fingerswith precise cam contours. Thus, this shifting device also requires acomplex production process and a high manufacturing cost. Moreover, asthe shift drive shaft extends in a direction perpendicular to thesliding selector shafts, and also perpendicular to the direction of thefork guide rails as well. Accordingly, due to this perpendiculararrangement of the shift drive shaft relative to the fork guide rails,this shifting device also requires a relatively large volume, and it isgenerally difficult to reduce the size of the shifting device, and thus,the overall transmission as well.

SUMMARY OF THE INVENTION

In order to solve the above described drawbacks and other problems ofthe conventional gear shifting device, the present invention provides anew and useful gear shifting device and methods for shifting gear ratiosfor a dual clutch transmission.

The present invention also provides a useful gear shifting device thatcan be provided with relatively low cost in comparison to theconventional gear shifting devices, and methods for shifting gears(i.e., gear ratios) preferably for a dual clutch transmission using orgenerally in association with the gear shifting device of the invention.

Moreover, contrary to the afore-mentioned conventional shifting deviceshaving a perpendicular arrangement relative to the fork guide rails, theshifting mechanism of the present invention is placed in parallelrelation with the direction of the fork guide rails. Thus, the shiftingdevice of the invention can simplify the design, reduce the length ofthe very long shift forks of the conventional design, and also reducethe vertical height and volume of the resultant transmission package.

According to one aspect of the invention, the gear shifting devicecomprises:

at least one guide rail each extending in a longitudinal axis thereof;

a plurality of shift effecting members (for example, such as shift forksor the like) configured to move a plurality of corresponding slidingsleeves coupled to the guide rail for shifting gears upon actuation of ashift actuator, the shift effecting members each having a terminal endportion with a finger receiving opening formed therein, the fingerreceiving opening extending in a direction generally parallel to thelongitudinal axis of the guide rail; and

a shift shaft extending in a direction generally parallel to thelongitudinal axis of the guide rail, the shift shaft having a shiftfinger coupled thereto;

wherein the shift shaft is rotatable to pivotally position the shiftfinger at locations aligned with the finger receiving openings of theshift effecting members, and is also displaceable in the longitudinaldirection in the finger receiving openings to move the shift effectingmembers to effect a gear shifting operation.

In one preferred embodiment, the gear shifting device is configured tocouple with a dual clutch transmission containing two clutches, one fordriving the odd numbered gears and the other clutch for the evennumbered gears. The finger receiving openings of the shift effectingmembers have, preferably, a generally rectangular shape, in which thefinger receiving openings of the two inner terminal end portions have anopening width which is larger than that of the finger receiving openingsof the two outer terminal end portions.

According to another aspect of the invention, the method of shiftinggears with a gear shifting device comprises:

providing a gear shifting device, which includes: at least one guiderail each extending in a longitudinal axis thereof; a plurality of shifteffecting members (for example, such as shift forks or the like) forshifting gears, the shift effecting members each having a terminal endportion with a finger receiving opening formed therein; and a shiftshaft extending in a direction generally parallel to the longitudinalaxis of the guide rail, the shift shaft having a shift finger coupledthereto;

rotating the shift shaft and pivotally positioning the shift finger at alocation aligned to receive in the finger receiving opening of aselected one among the shift effecting members; and

displacing the shift shaft in the longitudinal direction and moving theselected shift effecting member to effect a gear shifting operation.

In one preferred embodiment, said rotation of the shift shaft isactuated by a first electric motor, and said longitudinal displacementof the shift shaft is actuated by a second electric motor. The gearshifting operation is performed preferably via at least one slidingsleeve each coupled to the guide rail and the shift effecting members,and the gear shifting device is coupled preferably with a dual clutchtransmission containing two clutches.

BRIEF DESCRIPTION OF THE DRAWINGS

The above described and other objects, features and advantages of thepresent invention will be more apparent from the presently preferredembodiments of the invention disclosed in the following description andillustrated in the accompanying drawings, in which:

FIG. 1 illustrates one example of a dual clutch transmission to whichthe gear shifting device of the present invention is incorporated;

FIG. 2 shows a side cross-sectional view of the dual clutch transmissionof FIG. 1;

FIG. 3 a is a schematic perspective view, shown in part, forillustrating the operating portions of a conventional gear shiftingdevice;

FIG. 3 b is a top view of the conventional gear shifting device of FIG.3 a;

FIG. 3 c is a cross-sectional view of the conventional gear shiftingdevice, taken along line A-A of FIG. 3 b;

FIG. 4 a is a schematic perspective view, shown in part, forillustrating the general appearance of operating portions of the gearshifting device according to the present invention;

FIG. 4 b is a left side view of the gear shifting device of the presentinvention of FIG. 4 a;

FIG. 4 c is a cross-sectional view of the gear shifting device of theinvention, taken along line A-A of FIG. 4 b, and illustrating a positionwith the shift finger in neutral position;

FIG. 4 d is a cross-sectional view similar to FIG. 4 c, furtherillustrating the angular pivot positions of the shift finger relative tothe terminal end portions of the shift forks;

FIG. 5 is a perspective view illustrating one preferred embodiment ofthe gear shifting device of the invention;

FIG. 6 is a perspective view illustrating the structure of the shiftforks of the gear shifting device of FIG. 5;

FIG. 7 a is a front view of the gear shifting device of FIG. 5;

FIG. 7 b is a side cross-sectional view of the gear shifting device ofFIG. 5, taken along line A-A of FIG. 7 a and illustrating only the gear“selecting” portions of the gear shifting device;

FIG. 7 c is a side cross-sectional view of the gear shifting device ofFIG. 5, taken along line B-B of FIG. 7 a and illustrating only the gear“shifting” portions of the gear shifting device;

FIG. 8 a is a view similar to FIG. 7 b for illustrating the operation ofthe gear “selecting” portions of the gear shifting device;

FIG. 8 b is a front view for illustrating the gear “selecting”sub-operation of the gear shifting device;

FIG. 8 c is an enlarged view for section A of FIG. 8 b, showing thedetails of the shift finger and the terminal end portions of the gearshift forks, and further illustrating the gear selecting sub-operationof the gear shifting device;

FIG. 9 a is a sectional view illustrating the gear “shifting”sub-operation of the gear shifting device and showing the movement of ashift fork in one direction;

FIG. 9 b is a sectional view illustrating the gear shiftingsub-operation of the gear shifting device and showing the movement ofthe shift fork in opposite direction;

FIG. 10 illustrates one example of the operation of the inventionshowing a stage with the fourth gear engaged to drive the vehicle withthe fourth gear, in which FIGS. 10( a) and 10(b) are sectional viewssimilar to FIGS. 4( c) and 4(b), respectively, and illustrating theposition of shift finger received in the opening of the shift fork forthe second and fourth gears, and FIG. 10( c) is a partial sectional viewillustrating the corresponding positioning of the sleeves with thefourth gear engaged;

FIG. 11 illustrates a successive stage from FIG. 10 with the fourth gearstill engaged and the fifth gear preselected, in which FIGS. 11( a) and11(b) are sectional views similar to FIGS. 4( c) and 4(b), respectively,and illustrating the position of shift finger moved to engage with thefifth pre-selected gear, and FIG. 11( c) is a partial sectional viewillustrating the corresponding positioning of the sleeves (with thefourth gear still engaged and the fifth gear pre-selected);

FIG. 12 illustrates a successive stage from FIG. 11 with the fifth gearengaged and the fourth gear disengaged, in which FIGS. 12( a) and 12(b)are sectional views similar to FIGS. 4( c) and 4(b), respectively, andillustrating the position of shift finger moved to disengage the fourthgear, and FIG. 12( c) is a partial sectional view illustrating thecorresponding positioning of the sleeves (with the fourth geardisengaged and the fifth gear still engaged);

FIG. 13 illustrates a stage in which the vehicle is driven with thefifth gear engaged, in which FIGS. 13( a) and 13(b) are sectional viewssimilar to FIGS. 4( c) and 4(b), respectively, and illustrating theposition of shift finger in stationary position, and FIG. 13( c) is apartial sectional view illustrating the corresponding positioning of thesleeves (with the fifth gear still engaged);

FIG. 14 illustrates a successive stage from FIG. 13 with the fifth gearstill engaged and the fourth gear pre-selected, in which FIGS. 14( a)and 14(b) are sectional views similar to FIGS. 4( c) and 4(b),respectively, and illustrating the position of shift finger moved topre-select the fourth gear, and FIG. 14( c) is a partial sectional viewillustrating the corresponding positioning of the sleeves (with thefourth gear pre-selected and the fifth gear still engaged); and

FIG. 15 illustrates a successive stage from FIG. 14 with the fifth geardisengaged and the fourth gear engaged, in which FIGS. 15( a) and 15(b)are sectional views similar to FIGS. 4( c) and 4(b), respectively, andillustrating the position of shift finger moved to disengage the fifthgear, and FIG. 15( c) is a partial sectional view illustrating thecorresponding positioning of the sleeves (with the fifth gear disengagedand the fourth gear engaged).

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention are described herein withreference to the drawings. Throughout the drawings and associateddescriptions of the present application, common or similar elements areto be referred with the same or similar reference characters forsimplicity purposes.

FIGS. 1 and 2 illustrate one example of a transmission, in particular, adual or double clutch transmission, to which the gear shifting device ofthe present invention is incorporated. The dual clutch transmission isdesigned to have six gear speeds with two clutches 2 a and 2 b coupledwith two input shafts 6 and 7 to drive the gear train 4 installedbetween the two input shafts 6 and 7 and two output shafts 8 and 9. Thedual clutch transmission includes a dual clutch actuator 1, and a dualclutch assembly 2 which contains a first clutch (“clutch A”) 2 a fordriving the odd numbered gears (e.g., first gear 41, third gear 43, andfifth gear 45) and a second clutch (“clutch B”) 2 b for driving the evennumbered gears (e.g., second gear 42, fourth gear 44, sixth gear 46) andreverse gear 47 in response to actuation by the dual clutch actuator 1.The transmission may further include a dual mass flywheel 5 tofacilitate a stable and non-fluctuating operation of the transmission.

In order to perform the gear shifting process, the transmission of theinvention further includes a gear shift actuating device (to bedescribed below in detail) coupled thereto, which is driven by a gearshift actuator such as an electric motor. To activate the gear shiftingin accordance with operation of the actuator, a plurality of slidingsleeves 48-51 are further provided. In this embodiment, sleeve 48 is forshifting between the first and third gears, sleeve 49 for shiftingbetween the second and fourth gears, sleeve 50 for shifting into thefifth gear, and sleeve 51 for shifting between the sixth and reversegears.

In order to mimic an automatic transmission with seamless gear shifting,the dual clutch transmission enables a “pre-selection” of one gear amongmultiple gears by allowing the shifter to engage a non-driven gear whilethe vehicle is driving with another gear engaged. For example, whenstarting the vehicle, the transmission is in first gear (41) with clutch“A” (2 a) applied, and clutch “B” (2 b) is released. To shift intosecond gear (42), the shifter pre-selects the second gear (42), which isidle. Clutch A (2 a) is then released, and clutch B (2 b) is applied todrive with the second gear (42). The first gear (41) is then disengagedwhile the transmission is driving in second gear (42). To continue thesequence and shift to third gear (43), the third gear (43) ispre-selected. Then clutch B (2 b) is released, and clutch A (2 a) isapplied. The second gear (42) is then disengaged. This sequence proceedsautomatically and up to the maximum gear step of the vehicle, forexample, the sixth gear (46).

With reference to FIGS. 4 a-4 d, one preferred embodiment of the gearshift operating mechanism for the gear shift actuating device isdescribed herein in detail. In this embodiment, the gear shift actuatingdevice includes a plurality of shift effecting members, for example,such as shift forks 401, 402, 403, and 404 (as shown in FIGS. 5 and 6),that are configured to move the sliding sleeves 48-51 for the gear shiftoperation, of which shift forks only the actuating end portions 401 a,402 a, 403 a, and 404 a formed at terminal ends of the shift forks areshown in FIG. 4 a in order to explain the gear shifting mechanism withsimplicity. The gear shift actuating device further includes shift shaft410 which is configured to pivot or swivel around the longitudinal axisof the shift shaft for locating shift finger 416 of the shift shaft 410at predetermined pivot positions to select a particular actuating endportion 401 a, 402 a, 403 a, or 404 a of the shift effecting members(e.g., shift forks) for the intended shift operation of the gears, andalso configured to reciprocate in the axial direction for moving theselected shift fork in the axial direction to execute the shiftingoperation of the shift fork and the gear. In FIGS. 4 a and 4 b, theshift finger 416 is shown to be in neutral position (at 0° position)between the terminal end elements 402 a and 403 a of shift forks 402 and403.

As shown in FIG. 4 a, each of the terminal end elements 401 a, 402 a,403 a, and 404 a of the shift forks has a finger receiving groove oropening 430 a or 430 b to receive the shift finger 416 in the opening.Contrary to the conventional shift device shown in FIG. 3 c which hasthe same width 331 a for the cam groove 306 of each shift frame 301-304,the finger receiving opening 430 a for the first and fourth shift forks401 and 404 has a smaller opening width 431 a, and the finger receivingopening 430 b for the second and third shift forks 402 and 403 has alarger opening width 431 b (see FIGS. 4 a and 4 c). The size of thesmaller opening width 431 a is preferably a little (e.g., 0.0-2.5 mm)larger than two times the width 432 a of the shift finger 416, and thesize of the larger opening width 431 b is preferably a little (e.g.,0.0-2.5 mm) larger than three times the width 432 a of the shift finger416. In this manner, since the opening sizes of two inner terminal endelements 402 a and 403 a of the shift forks have a relatively largerdimension than those of two outer end elements 401 a and 404 a, themovement of the shift fingers 416 between the openings 430 a and 430 bof the shift forks can be effectively and easily made in order tocontrol the gear shifting operation, as will be described below infurther details.

Moreover, the shift finger 416 has a simple shape, for example, such asa rectangular bar shape as shown in FIG. 4 a or a cylindrical or ovalshape (not shown), and the finger receiving openings 430 a and 430 balso have a simple shape, for example, such as a rectangular opening asshown in FIG. 4 a, or the like. Therefore, the gear shift actuatingdevice of the present invention can be produced easily with relativelylow cost than the conventional shift device having complex andprecisely-made cam parts as shown in FIG. 3 a, for example. Moreover, inthe present invention the gear engagement and disengagement operationscan be executed with simplified control by the same shift finger 416.This is contrary to the conventional shift devices described above inconnection with FIGS. 3 a-3 c, which require a relatively complexcontrol with multiple activation elements, namely, with shift finger 316for gear engagement operation and with separate elements (i.e., aplurality of disengagement cams 316 a) for gear disengagement operation.As such, the gear shift actuating operation of the present invention canbe controlled more easily than the conventional shift devices of knowntypes.

Furthermore, contrary to the afore-mentioned conventional shiftingdevices (see FIG. 3 a) having a perpendicular arrangement of the driveshaft 315 relative to the axis of the fork guide rails, the shiftingmechanism of the present invention (see FIGS. 4 a and 5-7) is placed inparallel relation with the direction of the fork guide rails. Thus, theshifting device of the invention can simplify the design, reduce thelength of the very long shift forks of the conventional design, and alsoreduce the vertical height and volume of the resultant transmissionpackage.

Referring to FIGS. 4 b and 4 d, the angular positioning and movement ofthe shifter is described herein. The end elements 401 a-404 a (of shiftforks 401-404) are displaced angularly by the same angle. In anexemplary embodiment as shown in FIGS. 4 b and 4 d, the four endelements 401 a-404 a are arranged in a circular pattern with 60° angulardisplacement between the adjacent ones. Thus, when the horizontal angleis set to 0° position, the end element 401 a (of shift fork 401) islocated at minus(−) 90° position, the end element 402 a (of shift fork402) at minus(−) 30° position, the end element 403 a (of shift fork 403)at 30° position, and the end element 404 a (of shift fork 404) at 90°position. Here, the shift finger 416 is shown to be positioned inneutral location with 0° angular position. The actuator, in particular,the shift motor (to be described below) for angular movement of theshift finger 416, is designed to rotate or swivel the shift shaft 410(consequently, the shift finger 416 as well) in the same increment of,preferably, 30° per step. Thus, in this embodiment, when the shiftfinger 416 is positioned at −90° position (416 a), −30° position (416b), 30° position (416 c), or 90° position (416 d), it can engage withthe end elements 401 a, 402 a, 403 a, and 404 a, respectively, to shiftthe selected shift forks for engaging and disengaging the selectedgears. However, if the shift finger 416 is positioned at −60° position(416 e), 0° position (416 f), or 60° position (416 g), it idles and doesnot actuate any shifting of the shift forks even though it reciprocatesin the axial direction of the shift shaft 410.

With reference to FIGS. 5, 6, and 7 a, a preferred embodiment of thegear shifting device of the invention is described herein in furtherdetails.

The gear shifting device includes two actuators, namely, gear selectormotor 412 and gear shift motor 411 positioned in the proximity of eachother, and preferably, in parallel relation to each other and to thefork guide rails (450, 451) as well, in order to actuate the gear shiftoperation (to be described below in further details). The gear shiftingdevice further includes reduction gear box 413 with gears arrangedtherein for the gear shift operation, and two parallel guide rails 450and 451 disposed preferably in parallel relation with the two actuators411 and 412. Shift fork 401 and shift fork 402 are slidably arranged onthe first guide rail 450, and shift fork 403 and shift fork 404 areslidably arranged on the second guide rail 451, in which shift fork 401is for shifting between the first and third gears, shift fork 402 forthe second and fourth gears, shift fork 403 for the fifth gear, andshift fork 404 for the sixth and reverse gears. The shift device mayfurther include spring-loaded detents 405, 406, 407, 408 to engage withmultiple notches 401 n-404 n of the shift forks 401-401 mounted in thetransmission housing and configured to hold the shift forks in theselected axial positions (among the neutral position and the engagementpositions) until the shift finger 416 moves the shift fork to the nextgear.

With reference to FIG. 7 a through FIG. 9 b, the gear shifting operation(comprised of the gear “selecting” sub-operation and the gear “shifting”sub-operation described below) and structural elements for theoperations are described herein in detail. In the following disclosure,the gear “selecting” portions and the gear “selecting” sub-operation arereferred to the parts (and associated operations thereof) which performthe selection of a particular shift fork among multiple forks 401-404through the pivotal or swivel movement of the shift finger 416. Inaddition, the gear “shifting” portions and “shifting” sub-operation arereferred to the parts (and associated operations thereof) which performthe ultimate engagement (and disengagement) operation of a selected gearthrough the axial movement of the shift finger 416 to effect the gearshift, and subsequently to the aforementioned “selecting” sub-operation.

Referring now to FIGS. 7 a, 7 b, 8 a-8 c, the gear “selecting” portionsof the gear shifting device and the gear “selecting” sub-operation aredescribed in further details. As shown in FIG. 7 b (which is a sidecross-sectional view of the gear shifting device of FIG. 5, taken alongline A-A of FIG. 7 a), the gear selecting portions of the gear shiftingdevice includes gear selection actuator or motor 412, reduction gear 415installed thereto for gear selecting sub-operation, and shift shaft 418operably coupled to the reduction gear 415 and configured to pivotallyrotate the shift finger 416 for the gear selecting sub-operation (seeFIG. 8 a). As mentioned above and shown in FIGS. 8 b and 8 c, theselector motor 412 is designed to pivotally rotate the shift shaft 410(and the shift finger 416 as well) in the same increment of, preferably,30° per step. Thus, when the shift finger 416 is positioned at −90°position, −30° position, 30° position, or 90° position, it can select orengage with the end elements 401 a, 402 a, 403 a, and 404 a,respectively, to shift the selected shift forks 401-404 for thesubsequent engaging and disengaging sub-operation for the selected gears(as will be described below). However, if the shift finger 416 ispositioned at neutral positions, namely, at −60° position, 0° position,or 60° position, it idles and does not effect any shifting of the shiftforks even though it reciprocates in the axial direction of the shiftshaft 410. FIG. 8 c illustrates a state when the shift finger 416 isaligned with the first end element 401 a (in solid line) of the shiftfork, with other alignment states shown in broken lines to facilitateunderstanding of the selecting sub-operation.

Referring now to FIGS. 7 a, 7 c, 9 a, 9 b, the gear “shifting” portionsof the gear shifting device and the gear “shifting” sub-operation aredescribed in further details. As shown in FIG. 7 c (which is a sidecross-sectional view of the gear shifting device of FIG. 5, taken alongline B-B of FIG. 7 a), the gear shifting portions of the gear shiftingdevice includes gear shift actuator or motor 411, reduction gear 414installed thereto for gear shift sub-operation, and ball screw 419operably coupled to the reduction gear 414 and configured to move theshift finger 416 in axial direction for the gear shifting sub-operation(see FIGS. 9 a and 9 b). In particular, as shown in FIG. 9 a, when thegear shift motor 411 rotates in one direction (e.g., counter-clockwisedirection) by controller (not shown) of the vehicle, the shift finger416 moves axially in direction 416 h by operation of a shift fingerdrive means, in particular, ball screw shaft 417 coupled with ball screw419, and as a result, the shift finger 416 pushes the terminal endelement of selected shift fork (for example, shift fork 402 as shown inFIG. 9 a) in the manner as described above in connection with FIGS. 4 aand 4 c. As consequence, the sleeve 49 coupled to the selected shiftfork (for example, sleeve 49 for second gear 42 and fourth gear 44 asshown) moves in the same axial direction 416 h, and concludes the shiftoperation to a target gear (e.g., second gear 42) selected orpre-selected in a manner described above.

On the other hand, as shown in FIG. 9 b, when the gear shift motor 411rotates in an opposite direction (e.g., clockwise direction) bycontrolled by the controller of the vehicle, the shift finger 416 movesaxially in the other direction 416 i by operation of ball screw shaft417 coupled with ball screw 419, and as a result, the shift finger 416pushes the terminal end element of selected shift fork (for example,shift fork 402 as shown in FIG. 9 b) in the direction 416 i in themanner as described above in connection with FIGS. 4 a and 4 c. Asconsequence, the sleeve 49 coupled to the selected shift fork (forexample, sleeve 49 for second gear 42 and fourth gear 44 as shown) movesin the axial direction 416 h, and concludes the shift operation toanother gear (e.g., fourth gear 44). The above described operations areexplained in association with only the shift fork 402 (for second gear42 and fourth gear 44) for illustrative purposes. However, it is notedthat the shifting operations for other gears can be performed in thesame or equivalent manner described above.

With reference to FIGS. 10-15, the gear shifting operation utilizing thegear shifting device of the invention are further described herein, inwhich FIGS. 10-12 illustrate an example of gear up-shifting sequence,and FIGS. 13-15 illustrate an example of gear down-shifting sequence.

FIG. 10 illustrates one exemplary stage in which the fourth gear isengaged to drive the vehicle with the fourth gear. As shown in FIGS. 10(a) and 10(c), in this stage the shift fork 402 (for the second andfourth gears) is in the position such that the fourth gear 44 is engagedby the sliding sleeve 49 a to drive the vehicle with the fourth gear,and as shown in FIGS. 10( a) and 10(b), the shift finger 416 is receivedin the opening of the shift fork 402 for the second and fourth gears andlocated in a stationary position while waiting next command signals fromthe controller (not shown) of the vehicle. In this stage, “clutch B” ofthe dual clutch transmission (which is assigned to drive the evennumbered gears as described above) is applied while “clutch A” released,and the vehicle is driving with the fourth gear 44.

As illustrated in FIG. 11, when the controller delivers a command forpre-selecting the fifth gear 45 in order to prepare an up-shifting tothe upper gear, the gear selector motor 412 and the gear shift motor 411actuate the shift finger 416 to move it along the shift path 431 (FIG.11( a)) in the manner as described above, and move the sleeve 49 b toengage with the fifth gear 45 (FIG. 11(c)). Here, the vehicle is stilldriving with the fourth gear 44 since the clutch B is still applied,with clutch A (for odd number gears) released. This is a “pre-selection”of fifth gear.

Now, when the controller delivers a gear shifting command to drive withthe fifth gear in accordance with the control of automatic controller(or alternatively upon manual shift operation by the driver), the gearselector motor 412 and the gear shift motor 411 actuate the shift finger416 to move it along the shift path 432 (FIG. 12( a)), and move thesleeve 49 a and release it from the fourth gear 44 (FIG. 12( c)). Then,the clutch B is released, and clutch A (for odd number gears) is appliedinstantaneously (e.g., in a fraction of a second), and the vehicle ischanged to drive with the fifth gear 45.

The above described operations are explained in association withup-shifting between the fourth and fifth gears. However, it is notedthat the up-shifting operations for other gears (e.g., between 1^(st)and 2^(nd) gears, 2^(nd) and 3^(rd) gears, 3^(rd) and 4^(th) gears,5^(th) and 6^(th) gears, etc.) can be performed in the same or similarmanner as described above.

With reference now to FIGS. 13-15, the down-shifting operation of theinvention are described herein.

FIG. 13 illustrates a stage in which the fifth gear is engaged to drivethe vehicle with the fifth gear. As shown in FIGS. 13( a) and 13(c), inthis stage the shift fork 403 (for the fifth gear) is in the positionsuch that the fifth gear 45 is engaged by the sliding sleeve 49 b todrive the vehicle with the fifth gear, and as shown in FIGS. 13( a) and13(b), the shift finger 416 is received in the opening of the shift fork403 for the fifth gear and located in a stationary position whilewaiting next command signals from the controller (not shown) of thevehicle. In this stage, “clutch A” of the dual clutch transmission(which is assigned to drive the odd numbered gears) is applied while“clutch B” released, and the vehicle is driving with the fifth gear 45.

As illustrated in FIG. 14, when the controller delivers a command forpre-selecting the fourth gear 44 in order to prepare a down-shifting tothe lower gear, the gear selector motor 412 and the gear shift motor 411actuate the shift finger 416 to move it along the shift path 433 (FIG.14( a)), and move the sleeve 49 a to engage with the fourth gear 44(FIG. 14( c)). Here, the vehicle is still driving with the fifth gear 45since the clutch A (for odd number gears) is still applied, with clutchB (for even number gears) released. This is a “pre-selection” of fourthgear.

Now, when the controller delivers a gear shifting command to drive withthe fourth gear in accordance with the control of automatic controller(or alternatively upon manual shift operation by the driver), the gearselector motor 412 and the gear shift motor 411 actuate the shift finger416 to move it along the shift path 434 (FIG. 15( a)), and move thesleeve 49 b and release it from the fifth gear 45 (FIG. 15( c)). Then,the clutch A (for odd number gears) is released, and clutch B (for evennumber gears) is applied instantaneously (e.g., in a fraction of asecond), and the vehicle is changed to drive with the fourth gear 44.

The above described operations are explained in association withdown-shifting between the fifth and fourth gears. However, it is notedthat the down-shifting operations for other gears (e.g., between 6^(th)and 5^(th) gears, 4^(th) and 3^(rd) gears, 3^(rd) and 2^(nd) gears,2^(nd) and 1^(st) gears, etc.) can be performed in the same or similarmanner as described above.

As described above, the gear shifting devices of the invention andmethods for shifting gear ratios in a transmission are illustrated anddescribed above with several exemplary or currently preferredembodiments thereof, in particular, in connection with a dual clutchtransmission of a vehicle. However, the present invention is not limitedthereto, and is also applicable to other types of transmissions, forexample, such as automatic transmissions and manual transmissions withor without modifications to the structures and operating methodsdescribed above.

The above disclosed embodiments of the invention are representatives ofa presently preferred form of the invention, but are intended to beillustrative rather than definitive thereof. Accordingly, those skilledin the art will appreciate or recognize that various modifications andsubstitutions can be made thereto without departing from the spirit andscope of the present invention as set forth in the appended claims.

What is claimed is:
 1. A gear shifting device comprising: at least oneguide rail each extending in a longitudinal axis thereof; a plurality ofshift effecting members coupled to the guide rail and configured to movea plurality of corresponding sliding sleeves for shifting gears uponactuation of a shift actuator, the shift effecting members each having aterminal end portion with a finger receiving opening formed therein, thefinger receiving opening extending in a direction generally parallel tothe longitudinal axis of the guide rail; and a shift shaft extending ina direction generally parallel to the longitudinal axis of the guiderail, the shift shaft having a shift finger coupled thereto; wherein theshift shaft is rotatable to pivotally position the shift finger atlocations aligned with the finger receiving openings of the shifteffecting members, and is also displaceable in the longitudinaldirection in the finger receiving openings to move the shift effectingmembers to effect a gear shifting operation, wherein the shift actuatorincludes two motors, one for rotating the shift finger and the other fordisplacing the shift finger in the longitudinal direction, and whereinthe two motors are coupled with a shift finger drive means, and rotatingshafts of the two motors and a longitudinal shaft of the shift fingerdrive means are in generally parallel alignment with the longitudinalaxis of the guide rail.
 2. The gear shifting device as claimed in claim1, wherein the gear shifting device is configured to couple with a dualclutch transmission containing two clutches.
 3. The gear shifting deviceas claimed in claim 2, wherein, among said two clutches, one clutch isfor driving the odd numbered gears and the other clutch is for the evennumbered gears.
 4. The gear shifting device as claimed in claim 1,wherein said at least one guide rail includes first and second guiderails disposed in parallel with each other, and said shift effectingmembers include four shift forks, two slidably coupled to the firstguide rail and two slidably coupled to the second guide rail.
 5. Thegear shifting device as claimed in claim 4, wherein each of the fourshift forks is assigned to effect one or two gears with nonconsecutivegear numbers.
 6. The gear shifting device as claimed in claim 5,wherein, among the four shift forks, the first shift fork is for thefirst and third gears, the second shift fork for the second and fourthgears, the third shift fork for the fifth gear, and the fourth shiftfork for the sixth and reverse gears.
 7. The gear shifting device asclaimed in claim 5, wherein the gear shifting device is configured tocouple with a dual clutch transmission containing two clutches, one fordriving the odd numbered gears and the other for driving the evennumbered gears.
 8. The gear shifting device as claimed in claim 1,wherein the finger receiving opening of each shift effecting member hasa generally rectangular shape.
 9. The gear shifting device as claimed inclaim 1, wherein the shift effecting members include four shifteffecting members, each having the terminal end portion with the fingerreceiving opening, and wherein the terminal end portions of the fourshift effecting members are arranged in a circular pattern with constantangular displacement between adjacent ones.
 10. The gear shifting deviceas claimed in claim 1, wherein the shift finger drive means includes aball screw.
 11. The gear shifting device as claimed in claim 10, furtherincluding a plurality of detents configured to hold the shift forks inpredetermined axial positions.
 12. A gear shifting device comprising: atleast one guide rail each extending in a longitudinal axis thereof; aplurality of shift effecting members coupled to the guide rail andconfigured to move a plurality of corresponding sliding sleeves forshifting gears upon actuation of a shift actuator, the shift effectingmembers each having a terminal end portion with a finger receivingopening formed therein, the finger receiving opening extending in adirection generally parallel to the longitudinal axis of the guide rail;and a shift shaft extending in a direction generally parallel to thelongitudinal axis of the guide rail, the shift shaft having a shiftfinger coupled thereto; wherein the shift shaft is rotatable topivotally position the shift finger at locations aligned with the fingerreceiving openings of the shift effecting members, and is alsodisplaceable in the longitudinal direction in the finger receivingopenings to move the shift effecting members to effect a gear shiftingoperation, wherein the shift effecting members include four shifteffecting members, each having the terminal end portion with the fingerreceiving opening, and wherein the terminal end portions of the fourshift effecting members are arranged in a circular pattern with constantangular displacement between adjacent ones, wherein the finger receivingopenings of two inner terminal end portions have an opening width whichis larger than that of the finger receiving openings of two outerterminal end portions.
 13. The gear shifting device as claimed in claim12, wherein the shift actuator for rotating the shift finger isconfigured to stop the shift finger at four positions each aligned withits corresponding finger receiving opening of the shift effectingmembers and at three positions between the four positions.